number of voters i talked to were not particularly happy to see trump going after bush. they said it was no one's fault and nothing they felt like the former president could have done to prevent this. >> as trump is stumping, there is something happening on twitter and talk shows, a feud as we mentioned with jeb bush in the darkest days with donald trump pointing fingers and bush defending his brother. dana bash reports. >> reporter: a political dual about america's catastrophe on 9/11, 2001 playing out in a very 2016 way, on twitter. donald trump tweeting today at jeb bush i'm fighting to make sure it doesn't happen again. jeb is too soft. that after bush had tweeted donald trump talks about foreign policy as though he's still on the apprentice. at issue. trump suggestions that jeb's brother george w. bush could have done more as president to prevent the september 11th terror attacks.